Changing ocean currents may affect global climate

Yale researchers have discovered that as a result of global warming, deep currents in the Atlantic Ocean may shift, leading to the rapid loss of sea ice in the Arctic Ocean.

Currently, southward-flowing water maintains the Atlantic Meridional Overturning Circulation, a collection of sea currents located deep in the ocean known by its acronym AMOC. But the study, published on Oct. 22 in the Nature Climate Change journal, found that due to rising carbon dioxide levels, the water will begin to flow northward — which may increase the melting rate of sea ice in the Arctic Ocean.

“Arctic ice loss is currently occurring at an alarming rate that exceeds any model predictions,” explained Matthew Thomas, a postdoctoral associate in the geology and geophysics department and the senior author of the study. “A northwards extension of the heat carried by the overturning circulation might be expected to further interact with Arctic ice and thereby precipitate climatic changes in the region — and consequently across the whole planet.”

Using various climate models, the researchers simulated the AMOC strength under global warming conditions which included carbon dioxide concentrations four times greater than the current concentration.

Thomas noted that a particularly unexpected finding was that a future source of deep water can come from within subtropical latitudes. Currently, water first re-emerges at higher latitudes before subsequently sinking. However, as the climate changes, the water may be prevented from re-emerging, thereby simply recirculating and flowing southwards once again.

“A weakening AMOC can lead to a sea level rise … East Coast regions are therefore more likely to experience the direct consequences of an AMOC weakening, such as stronger and more frequent flooding events,” Thomas said.

According to the study, the conclusion that changing ocean currents could lead to the rapid melting of Arctic Ice may have large implications for the rate and scale of climate change. In addition, the conclusion could lead to socioeconomic consequences including food, water and energy shortages in populated regions. Thomas said that the phenomenon may also affect people by causing hurricane activity, flooding or mass future climate migration.

Further research may assess how circulation changes affect ocean uptakes and the storage of heat and carbon, which have important consequences for climate change, Thomas added.

“Ultimately, we hope that the scientific findings will be acted on responsibly by policymakers by reducing our dependence on fossil fuels,” he said.

According to NASA, the average global temperature on Earth has increased by about 1.4 degrees Fahrenheit since 1880.